Telephone system



1,614,293 7 11 1927' H. M. FRIENDLY TELEPHONE SY STEM Filed March .5,1922 7 Sheets-Sheet l //a as Inveniurfierherfl l-Friendlg 11 1927' H. M.FRIENDLY TELEPIFIONE SYSTEM '7 Sheets-Sheet 2 /w kww Filed March 5, 1922I Inventor- Herh er'l-Pl-Friendl Pill-J5.

Jan. 11 1927- FRIENDLY TELEPHONE SYSTEM Filed March 5, 1922 '7Sheets-Sheet 5 1,614,293 Jan- 11 1927- FRIENDLY TELEPHONE SYSTEM FiledMarch 5. 1922 '7 Sheets-Sheet 4 :1 L v I: Inverfiur- S HerbEPi-MFFiEHdIH 1,614,293 11 1927' H. M. FRIENDLY TELEPHONE SYSTEM FiledMarch 5, 1922 7 Sheets-Sheet 5 I III' Inventur- Herbert-P'I-FriandlgAHLI Jan. 11, 1927. 1, 4,293

H. M. FRIENDLY TELEPHONE SYSTEM Filed March a. 1922 7 Sheets-Sheet 6Fig.5.

Inventur- Her]: art-PI-Friendlg ALILJ 11 1927' H. M. FRIENDLY TELEPHONESYSTEM Filed March 3, 1922 '7 Sheets-Sheet 7 0 i L i l M E Patented Jan.11, 1927.

3 UNITED STATES it tin HERBERT I. FRIEKDLY, OI POBTLAN D, OREGON.

TELEPHONE SYSTEM.

Application filed larch 8, 1922. Serial No. 540,719.

The present invention relates to automatic telephone systems in whichselector switches are employed. More specifically, the invention relatesto animproved method and apparatus whereby certain mechanism ofselectors is dispensed with, and a paratus units involving essentiallythe isplaced mechanism pirpvided. The a paratus units are arranged shthat they wil automatically associate themselves with a seized selector.Thus, when a selector becomes seized, by an antecedent line switch, forexample, if it is not at the time associated with an apparatus unitcooperative therewith, it will become forthwith so associated by reasonof the cooperative apparatus unit hunting for and seizing the saidseized selector. \Vhen a selector has an apparatus unit in seizedrelation with it, as referred to, the selector becomes directivelycontrollable as if it involved only permanently related componentelements.

In incorporating the present invention, 1 provide apparatus units insmaller number, one-twentieth as many, for example, as there areselector units, and provide each apparatus unit with a driving mechanismwhich will automatically initiate its functioning upon a cooperativeselector being seized by a line switch, and cause it to hunt over bankcontact sets until the said seized selector is found. It will not againhuntuntil a selector cooperative to the apparatus unit is thereafterseized. However, when the selector with which the apparatus unit becomesassociated in seized relation is caused to operate and select and seizea trunk of a called group, the embracing apparatus unit will becomeoperatively disassociated from the last said selector, so far as beingeffective to its linking conductors, or the operative functions thereofis concerned.- The apparatus unit thus contains control elements(relays, for example), which are adapted to be automatically temporarilyassociated with selector elements'to form a complete selector unit.

It will appear that because of eliminating certain elements of theselector units, the latter said units will-involve less cost andcarrying charges, and require less containing space. Also, clue to thesimplified arrangement, they will involve less maintenance, and,moreover, will admit of incorporating desirable operative functions (notincorporated in the exampled system), which due to cost of additionalelements, would not be lapping 'the connections between the groupsconduces toward a uniform distribution of the traffic, since there is alike relation between each line switch group and all selector groups.

In order to make the disclosure as simple and. brief as possible, Ihave'chosen a selector circuit, well known in the art, and haveintroduced such changes therein as are needed, in order for it tooperate in accordance with the present invention.

It will appear that the selectors involved in the present invention,wherein they are controlled by a temporarily associated apparatus unit,may be cooperated in seized relation with selectors of well known types,that is, may seize or be seized by selectors of well known type.However, the descripti'ons in the exampled system show the selector ofthe present invention seized by the line switch. In view of the factthat selectors of well known types seize under conditions similar tothose of line switches of the illustrated type, and introduce generallylike conditions into the linked circuits, the adaptation wherein aselector is substituted for the line switch will be manifest. Theselectors of the present invention may manifestly be employed toterminate trunks of any numerical order, and are therefore notrestricted to use to the first numerical order, as shown, by way ofexample.

Reference is made to my Patent No. 1,- 565,269, granted December 15,1925, on an application filed March 30, 1922, Ser. No. 548,165. Also,mypending application filed December 16, 1921, Ser. No. 522,842, and mypending application filed October 24, 1921, Ser. No. 510,016.

Referring to the drawings Fig. 1 is an apparatus unit A, and four of thecooperating bank contact sets of the present invention.

Fig. 2 is a selector B of the present invention, cooperative with A.

Fig. 3 is a selector C of the present invention, similar to selector Bcooperative with A Fig. 4 indicates a second selector S of well knowntype, cooperative with the first selectors B and C It also indicates aconhector C" of well known type, reached through the selector S. Theconnector C has access to the line leading to telephone 'l, and otherlines not shown.

Fig. 5 shows a substation telephone T leading to a line switch D Theline switch I) has access to selector B and other selec-.

Fig. 7 shows a diagrammatic layout of a portion of the exampled system,but showing an arrangement which may be alternatively employed withrelation to the apparatus units and respectively embraced selectors.

Fig. 8 shows a diagrammatic layout of a portion of the exampled systemwith relation to apparatus units and respectively embraced selectors.

Fig. 9 shows the assembly of the various figures to display the exampledsystem. Lines extendi'm toward adjacent margins which register are to beunderstood as extensions of the same line joining terminals. Linesextending toward margins which do not register with lines extendingtoward adjacent margins indicate multipled elements of those shown maybe attached.

The telephones T", T and T are of the general class, and in fact may beassumed as of the generally similar type as the telephone designated Ain U. S. Patent No. 13,901, reissued to Frank Newforth, April 13th,1915.

Line switches l) and E are of the general class as shown in U. S. PatentNo. 1,193,160, granted to Lamb, August 1st, 1916. They are of the exacttype shown in my pending application, Serial No. 510,016, filed October24th, 1921.

The first selectors B and C when cooperated in seized relation with theapparatus unit A, respectively, comprise a complete selector of thegeneral class shown in U. S. patent to Keith, Erickson & Erickson, No.815,321, granted March 13th, 1906, of course, modified in mechanical andcircuit details to operate on the Well known so-called two-wireprinciple, and in accordance with the present invention.

The second selector S may be assumed to be of the exact type as selectorE of the said cited patent to Newforth.

The connector C may be assumed to be of the exact type as connector H ofthe said cited patent to Newforth.

Referring further to Fig. 1, the apparatus unit A has access through itswipers and cooperating circumferentially spaced bank contact sets with aplurality of first selectors of which selectors B and C are two. thewipers of the said apparatus unit unit. In this connection it will beunderstood that while one only apparatus unit is shown cooperative withselectors B and G a plurality of such apparatus units may so cooperatethrough sets of corresponding bank contacts in multiple relation. Underthe latter method of operation all apparatus units would have commonrelation with all the embraced selectors and common conductors, thefirst apparatus unit to gain the seizure of a selector which has becomeseized by a line switch serving to set up a condition whereby theremaining apparatus unit or units will stop hunting. Under this lattermethod of relating a small plurality of apparatus units with a largerplurality of selectors the hunting time will be generally reduced, sincethe apparatus unit having its wipers nearest to the selectorrequiring anapparatus unit will be the one to seize. It will be noted that inintroducing a second or plurality of apparatus units; each embracing thesame group of selectors commonly, the resting contacts of armaturescorresponding to 112' will be multiply attached to conductor 215 inorder that the motor magnet as M of all idle apparatus units will beenergized responsive to a selector being seized by a line switch.Also,.the

grounded make contact cooperative with armature 176 of apparatus unit Awill be extended to armature corresponding to 176 of the next apparatusunit of the group; being continued in this manner to the armaturecorresponding to 176 of the last apparatus unit, which latter armaturecooperates'with a grounded working contact as shown in apparatus unit A.Thus, the conductor 216 will not become grounded to bar the idleselectors of the group embraced by said plurality of apparatus unitsunless the conductor 216 is chained to ground, as when a singleapparatus unit is employed as shown in the drawings illustrative of thesimplest embodiment.

By referring to Fig. 8, it will be noted that there are three groups ofline switches, F, G and H, each group of which contains three lineswitches. In commercial practice each group would perhaps contain threehundred line switches, terminating an equal number of respectivelycorresponding substation lines. Also, in commercial practice, in placeof there being three groups of line switches, there would perhaps betwenty groups. However, the numbers (3) shown in Fig. 8 will suffice toexemplify the present invention, without unduly involving the drawingsand descriptions. 1

With further reference to Fig. 8, it will be noted that substation Tleads to line Hm I switch 1') in group F, and that substation "l" leadsto line-switch -E-in-group H. will also be noted that the bank positionsg apparatus units and selector groups to be i in the line switches D andE numericallcorrcspond, though they are not multiple Of course, thisnumerical relation has no operative significance. beyond having auniformity in order to facilitate simplicity in the record system,looking towards ready tracing of connections. However, it will beobserved that the same apparatus unit A has access to the selectors Band C and also to other selectors belonging to other groups which areconnected to corresponding bank positions in the line switches of'theother groups. .That is to say, numerically corresponding bankcontact sets of thevarious groups of line switches refer to the samegroup of selectors. For example, should there be twenty groups of lineswitches each having twenty-five sets of bank contact"- there would betwenty-five groups of selectors. The same number of groups of selectorswould be employed if there were more or less line switch groups,

pends upon the number of sets of bank contacts of the line switches,each set of bank contacts corresponding to a group of selectors. It willthus appear, that the first set of bank cont-acts of all the line switchgroups correspond to the irst group of selectors. Similarly, the thirdset of bank contacts of all line switch groups correspond to the thirdgroup of selectors, etc. Generally, stated, there are a plurality ofline switch groups, each said group having access to a group ofselectors, wherein the numerically corresponding located selectors ofthe said selector groups (with respect to the bank contacts of the lineswitches) taken together, constitute a divisional group accessible to anapparatus unit. By way of still further explanation, each selector groupaccessible to or embraced, as it were, by an ap arat-us unit, containsone selector from eac selector group accessible to a group of lineswitches,.and therefore, each selector group accessible to a line switchgroup has in it one selector (or more, as will appear presently) of eachgroup embraced by each apparatus unit. However, attention is called toselector J accessible to the line switches of group H. The selector J isembraced by the apparatus unit A. The apparatus unit A therefore hasaccess to. two selectors reached through the. line switch group H. It ismanifestly possible to .have the ap paratus unit A embrace additionalselectors of the said group H, and in fact, additional selectors locatedin numerical correspondence with relation to the banks of the lineswitches in groups G and F, though the numerical correspondence willhave no operative significance, Under the method of S1I1.9 the number ofgroups of selectors de-- having an apparatus-unit embrace a. pluraflityof selectors accessible to a line switch group will, in eifect,"'reducethe number of employed, I assuming thatthe same number of selectorswould be embraced-b the apparatus unit in each case. The atter'describedalternative arrangement lends itself where a relatively small number offirst selectors are required to handle the traffic.

It will appear presently, that if a selector of any group is seized b ahunting line switch, all selectors of tlie group become temporarilybarred against seizure, by reason of a false busy condition beingthereby set-up with relation to the grou containing the seized selector.lector has been operated so that it seizes a called trunk, the set-upfalse busy condition becomes thereby removed, so that an idle selectorof the group is thereafter subject to seizure by a line switch of anygroup. It will be understood, in view of foregoing statements, thatcorresponding bank contacts of all line switches refer to a numericallycorresponding group of selectors, each group of selectors being commonlyembraced by an apparatus unit which will be enabled to be in cooperativerelation with but one of the selectors thereof at any time, and it willbe resting at the bank position corresponding to the last selector ofits embraced group employing it, from whence it will automaticallyfunction by way of hunting, when its subsequent requirement occurs.

lVhen a hunting line switch finds a set of bank contacts thereof busy,by reason of the corresponding selector being busy or due to a falsebusy condition being found, the corresponding set of bank contacts willbe passed over andthe successive set tested. It will appear presentlyhow, if any ap-. paratus unit is not free (that is, in a seized relationto a set of bank contacts, or is hunting), its embraced selectors willnot be subject to seizure by a line switch, but as soon as the apparatusunit becomes free any idle selectors embraced by it become subject toseizure.

Incidental to a selector becoming seized by a line switch, a ground isplaced upon a first common conductor of the group to guard otherselectors of the group,as well as the seized selector temporarily, andthis ground is maintained until the apparatus unit becomes free. Also,the seized selector, through the'actuation of its relay, resultant tothe seizure, applies a ground to another common conductor of the groupfor the purpose of initiating the hunting operation of the embracingapparatus unit. Under the condition of a selector being seized by a lineswitch, the embracing apparatus unit will be thus caused to hunt forandfind it, whereby the latter said selector will be thereafter When t1e secapacitated to function under directive control, and a tone will beap lied audible to the calling partyto index t e ready condition of'theselector, so directive impulses may be forthwith applied. The groundplaced upon the said first common conductor which temporarily guards thelast seized selector, becomes forthwith disassociated from the lastseized selector upon its relay actuating, the latter said selector beingthereafter guarded by ground on its private conductor attaching to theprivate bank contacts of accessible line switches. However, the saidfirst common conductor is maintained grounded from the selector, andalso, from the embracing apparatus unit when it seizes the selector, andthis ground is maintained until the selector seizes the trunk leading tothe second selector, through its relay fully actuating, or until thecall is destroyed before such actuation takes place.

In view of the fact that from the time aselector is seized by a lineswitch until the selector has been directively operated, and it hasthereafter seized a trunk, not more than 7 two seconds have elapsed, onthe average,

and infurther view of the fact that the selectors are thereafter held onthe average of say, eighty seconds before being released, it will appearthat one apparatus unit could possibly serve forty selectors. If enoughselectors are provided so there will always be an idle one available,the condition simply resolves itself into that of the line switch of acalling line finding a selector of a group having an idle apparatusunit, bearing in mind that successive sets of bank contacts hunted overby the line switch'each refer to a selector of corresponding differentselector groups, and that the same selector will not be tested twice,unless all groups are found busy and a re-testing occurs, the lineswitch continuing to hunt until an idle selector is found. However, thearrangement shown in Fig. 7 (also having in mind the disposition ofselector J referred to, and-which is different from the one about to bedescribed), contemplates that re-testing in a group shall occur byreason of the fact that selectors of the same group are interspersed.That is to say, if a selector of a group is encountered as busy, theline switch will testanother se-' lector of the same group after it hashunted over anumber of other selectors belonging to other groups. Forexample, the first, third and fifth set of bank contacts of the lineswitches refer to the same group of selectors, though not to theidentical selectors of the said groups. Of course, if a false busy isapplied to all the selectors of a group by reason of the apparatus unitembracing them being busy, all selectors of the group will test busy toa hunting line switch, as shown in the arrangement set forth in Fig. 8..

In comprehending the arrangement shown in Fig. 7, it will be rememberedthat the line switches have no normal resting position, and willtherefore rest where last employed, so that the wi ers of the variousline switches Willr be de oyed. over the entire group of accessible vthus the same selectors will not be tested for in a predetermined order,upon calls being initiated. s

Referring to selector B, it will be understood that the generalmechanical arrangement is the same as that ofselector. E-of the saidcited patent to Newforth. However, a set of off-normal springs R0 areprovided, which only operate when the shaft carrying the wipers rotateoff-normal. The set of off-normal s rings VO operate when the wipersstep ofi normal (vertically) primarily. The relay S which functlons as aswltching and a release relay, has two windings. The upper winding, whenenergized causes the relay to fully operate. The lower winding (due to'its high resistance and disposition), when alone energized servesJsooperate only the four armatures (209, 212, 211 and 213) shown in solidblack. Due to a restraining spring, the lower-most armature will notengage its make contact, thoughit will disengage its resting contact.The off-normal spring sets R0 and V0 in selector C correspond as tofunction with ank contact sets, and

sets R0 and V0 in selector B res ective-' 1y. Similarly, relay S and Shave t e same characteristics.

Having in mind the location of the equipment elements T, T, D E", B, Cand A, in Fig. 8, it will be assumed that a call is initiated atsubstation T A circuit path can be traced from the winding ofslowreleasing line relay 501, armature 502 line conductor 503, receiverof substation T I conductor 504, armature 505 to ground: relay 4 501actuating. Ifit is now assumed that the set of bank contacts 506 to 509(inclusive) upon which the wipers 512 to 515 of line swltch D are shownresting (respectively) is busy, because of the corresponding selector Bbeing busy by reason of it having been seized andheld due to apreviously initiated call, private bank contact 509, and its multiplesappearing correspondingly in other line switches of its group, willconstitute ground, as will appear presently. Under the latter conditiona circuit path will exist from the said grounded bank contact 509, wiper515, armatures 517, 518 and 519 to the winding of the motor magnet M thesaid motor magnet operating to interrupt the latter traced path in thewell known manner to cause the wipers 512 to 515 to be advanced intoengagementwith bank contacts 521 to 524, the latter corresponding to aselector similar to 13*, not shown. If bank contact 524 also constitutesground the motor magnet M will be caused" to furtheredllf,

line switch I) has its bank contact sets spaced radially and that itwill successively test in a hunting operation consequent to a call beinginitiated on its leading-in line. As has been referred to, and as willfurther appear presently, the line switch D will hunt and successivelytest wherein huntedover selectors may be idle, but falsely guardedagainst seizure.

It will be assumed that bank contacts 509 and 524 do not primarilyconstitute ground,

but that bank contact 506 (and 509) does constitute ground, due to afalsely set-up condition efiectuated from the apparatus unit A or anembraced selector thereof. In view of armature 525 being retracted,wipers 512 and 515 are electrically tied, so the functioning of the lineswitch will be the same, regardless of which wiper 512 or 515 primarilyreceives ground.

It will be assumed that the bank contacts 506 and 509 do not constituteground at the time the call is initiated, and therefore, ground will notbe applied to the winding of the motor magnet M which latter conditionnot only served to operatively encrgize the motor magnet, but applied aground short-circuit to the lower winding terminal of the switchingrelay 527, so that in View of the upper winding terminal thereofbeinggrounded on armature 528, it is disabled from becoming energized. Acircuit path can now be traced from the winding of motor magnet Marmature 519, winding of relay 527, to grounded armature 528, the relay527 actuating, the motor magnet M, due to its marginal adjustment, notoperating. The conductors 503 and 504 are thus continued througharmatures 502 and 505, wipers 513 and 514, bank contacts 507 and 508,conductors 531 and 532, respectively. At the time armature 517 attracts,ground is applied from armature 528, armature 517, wiper 515, bankcontact 509, conductor 533 (and multiples), oft-normal springs, upperwinding of relay S resistance r to grounded battery, the relay -Sactuating by way of operatively attracting all its armatures. Since thewipers 203 to 205- are free, the attracting of the armatures 206 to 208will have no operative effect at this juncture. Also, since theoft-normal spring set R0 is normal, the full attracting of thelowcr-most armature 209 will have no operative effect at this juncture.However, a momentary locking circuit path will be completed from thearmature 210, off-normal springs to the upper winding of relay S andalso to conductor 533. This momentarily locked condition of relay S willbe forthwith destroyed, causing all armatures, excepting ductor 216 tofalsely.

those shown in' solid black to retract, as will appear presently.- Thesaid ground is applied to conductor 533 before the relay 501 has hadtime-to deactuate, so that no lapse of ground occurs to conductor 533.The uppermost armature 211 being attracted, disconnects the conductorleading to bank contact 506 and its multi les from common conductor 216.Ground 1 rom armature 212 IS applied through'otf-normal contacts tocommon conductor 215, armatures 112, 113

and 114 to the winding of motor magnet M.

Ground from armature 212 is also applied through oft-normal contacts tocommon conguard the accessible line switches against seizing an idleselector of the group embraced by the apparatus unit A, as will appearpresently. However, a circuit path is coincidently completed with .thel-atter said paths from grounded off-normal spring, armature 213,conductor 214,

bank contact 126, wiper 146 to the windingof slightly slow-releasingrelay 148, the latter said relay actuating'to open the former tracedpath to the winding of the motor magnet M. Armatures 149, 150 and 181 onielay 148 are provided for an object which will appear presently.

In the last foregoing descriptions the apparatus unit A is in associatedrelation with the bank contact set thereof corresponding to the selectorB when the latter said se-' lector is seized. This condition will notusually occur, since ifthe apparatus unit embraces twenty selectors, forexample, there will be a possibility of one to twenty that the seizedselector will not have the embracing apparatus unit associated with itwhen seized, as is shown in the drawing with reference to selector B Theoperative functioning under the condition wherein the apparatus unit isnot in associated relation with the seized selector will be discussedpresently.

Going back to the condition ensuing incidental to the actuation .ofrelay 527, it will appear that a circuit path will be closed from theupper winding of relay 151, armature 152, wiper 135,'bank contact 115,conductors 153, 531, and over the path traced including the receiver atsubstation T conductors 532, 217, bank contact 125, wiper mature 210retracts, there will be no lapse of ground to conductor 533, so relay527 contact.

will remain actuated and the selector B guarded against seizure. Acircuit path can be traced from grounded armature 160, wiper 143, bankcontact 123, conductor 161 to the lower winding of relay S the lattersaid relay being now energizedby both its windings cumulatively.Armature 181 on relay 148 being attracted, ground will be appliedtherethrough, wiper 138, bank contact 118, conductor 172 to the liveterminal of the upper winding of relay S thus short- -circuiting thesaidupper Winding. In view of the short-circuited winding, andcharacteristics, the relay S is slow-releasing under the condition, thusallowing armature 160 to apply its ground to the lower winding of saidrelay S before the energizing path of relay 148 is opened by theretraction of armature 213, which latter does not occur at thisjuncture. However, all armatures, excepting those shown in solid blackdo retract, and the'lowermost (solid black) armature 209 does retractfrom its make The armature 158 attracts to apply ground to conductor 533before armature 210 retracts, so no lapse of ground occurs to conductor533, by reason of the upper winding of relay S being deenergized as setforth. The object of deenergizing the latter said winding of relay Swill appear presently.

It will be assumed that the first digit 1 is sent from the callingdevice at substation T causing relay 151 to deactuate and reactuate onetime'responsive thereto. Armature 163 will apply its ground to wiper144, bank contact 124, conductor 164, rotary orinormal springs,conductor 218, bank contact 120, wiper 140, armature 165 (relay 155sustaining, over the current'lapse), winding of slow-releasing seriesrelay 167, wiper 142, bank contact 122, conductor 168 to the verticalmagnet VM the latter said magnet operating by way of raising the shaftcarrying wipers 203 to 205 into alignment with the first level. of bankcontacts, the relay 167 actuating coincident with the magnet VM Armature169 will apply ground received from armature 158 to the winding oftheshunted interrupter relay 170, causing it to actuate. At the timerelay 170 actuates resultant to the relay 167 energizing, the verticaloff-normal springs V0 operate, opening the energizing path of relay 148,so that armature 181 retracts. However, armature 171 applies its groundbefore armature 181 retracts, insuring the maintenance of ground onconductor 172. The latter said grounded condition of conductor 172 isnow dependent upon relay 170 remaining locked (as will appear presently)to said conductor 17 2, which latter conductor is now grounded atarmature 171 of relay 170 in lieu of at armature 181 where it wasinitially applied.

Under the last foregoing condition, that of conductor 172 beinggrounded, the upper winding of relay S is unenergized, but the lowerwinding of relay S is energized, since armature 160 is attracted. Thearmatures of relay S excepting those shown in solid black are nowretracted, the lowermost armature 209 being retracted from its makecontact, but attracted from its resting contact. i

The relay 170 is locked by wayof armature 173, wiper 141, bank contact121, conductor 221, upper set of oil-normal springs, armature 220 togrounded conductor 172. Ifthe path is opened, as at armature 220,incidental to the actuation of the rotary magnet RM the relay 170 willdeactuate, armature 171 removing the ground from the conductor 172.However, ground applied through wiper 203 and retracted armature 206would serve to reground it upon the retraction of the said armature 220,whereupon the relay 170 will reactuate and lock through its armature171.

Upon armature 169 retracting, following the impulse to the verticalmagnet VM a circuit path can be traced from ground on armature 158,armatures 169, 174, wiper 139, bank contact 119, conductor 175 to therotary magnet EMF, the latter said magnet operat-' ing by way ofadvancing wipers 203 to 205 one rotary step into engagement with bankcontacts 223 to 225. Incidental to the rotary magnet operating, itsarmature 220 will open the described locking path for the relay 170, asreferred to, so the latter said relay will deactuate. Armature 209.being attracted from its resting contact, thou h the vertical off-normalset V0 is operate prevents-the release magnet Re from being energized.The armature 211 being attracted prevents the conductor leading to bankcontact 506 (and multiples) of the line switch D becoming grounded onconductor 216, the latter conductor now receiving ground througharmature 176 of the apparatus unit A.

It will be assumed for the present that the second selector S,corresponding to the set of bank contacts 223 to 225, is busy, and

therefore the bank contact 223 constitutes ground when engaged by wiper203. Un-

er such condition, when the wiper 203 receives ground from bank contact223 and armature 206 is then in a' retracted condition, the said groundserves to ground the live terminal of the upper winding of relay S atthe right-hand terminal of resistance 7' and to also apply this groundthrough armature 220 on the rotary magnet, vertical off-normal springs,conductor 221, bank contact 121, wiper 141, armature 173 to the windingof relay 170, the latter said relay actuating, whereupon a lockingcircuit for it becomes established over the before traced path, and inview of armature 169 being retracted, the rotary magnet RM will energizeoverthe before traced path, by way of advancing the wipers a furtherrotary step.- The cycles of functioning by way of automaticallyadvancing the wipers to successive sets of bank contacts re-occur untilthe wiper 203 fails to receive ground to maintain the ground on theright-hand terminal of resistance 1' and to reenergize the relay 170.When the wiper 203 fails to receive ground, the relay 17 will not becaused to re-actuate and cause the rotary'magnet RM to operate,

and moreover, the upper winding of relay S will energize over the beforetraced path to armature 156 and thereby effect the seizure of theselector B Going back to the condition wherein the wipers 203 to 205engaged bank contacts 223 to 225, and assume that the bank contact 223does not constitute ground. When the relay 170 unlocks consequent to theattraction of the armature 220 on the rotary magnet RM incidental to thefirst rotary movement of the wipers 203 to 205, the ground is therebyremoved from the right-hand terminal of resistance 1*, so that the upperwinding of relay S will become energized over the before traced path byway of armature 156, the selector B thus seizing. A circuit can now betraced from bank contact 224, conductor 230 to the upper (battery)winding of the line relay in second selector S, and from the lower(ground) winding of the said line relay, conductor 401 to bank contact225, so that due to armatures 207 and 208 being attracted, the receiverat substation T is now energized in series with the battery and groundwindings of the line relay ,of the selector S The release relay in theselector S will cause conductor 402 to project ground back to bankcontact 223, wiper 203, armature 206, conductor 157, free windingterminal of the upper winding of relay S maintaining the selector Bseized. The latter ground is applied before the armature 156 retracts,so no lapse of ground occurs to conductor 157. The armature 156 willretract, due to the fact that when armature 209 becomes fully attracted,its ground is applied through rotary off-normal springs, conductor 222,bank contact 127, wiper 147 to the winding of slow-releasing relay 179,causing the latter said relay to actuate to disassociatethe windings ofrelay 151 from talking conductors 531 and 532, whereupon the latter saidrelay will deactuate, followed by relay 155. It will be noted in thisconnection. that when armature 206 attracts, and while itis receivingground over conductor 402, a low battery potential will exist onconductor 172, which will be appliedthrough armature 220, up per set ofvertical oft-normal springs, conductor 221, bank contact 121, wiper 141,armature 173 to the winding of relay 170, but the current thus derivedthrough the winding of relay 170 is not sufiicient to operatively affectit. Armature 112 being now retracted. the motor magnet M will becomeoperatively energized consequent to any selector of the group embracedby the apparatus unit A becoming seized, whereby the common conductor215 will become grounded in the manner before described.

In this connection, attention is directed to the fact that when aline'switch as D is hunting over busy bank contact setr, wherein thewiper 515 receives ground, the wiper 512'will also receive ground, sincethe two latter said wipers are tied through armature 525. This will meanthat bank contacts engaged by wiper 512 will be grounded while the lineswitch is hunting. However, the latter grounding of bank contacts willhave no operative effect through the common conductor 216, from the factthat when the selector B corresponding to bank contact 506, for example,seized or remains seized, whereby the armature 211 of relay S isattracted, the conductor leading from bank contact 506 (and multiples),is opened. Under the condition of relay S being actuated, or theselector B is in a seized condition from a line switch, said selector Bwill be guarded against seizure, by reason of the ground applied toconductor 533 from armature 210, or from armature 158 of the apparatusunit A. Were it not for the provision of armature 211, hunting lineswitches of the group would apply ground received through the wiperthereof corresponding to 512, and the engaged bank contact to commonconductor 216, and from the latter conductor to'all contacts engageableto Wipers corresponding to 512. So that under the conditlon of a lineswitch hunting over busy bank contacts, it Wouldincident-ally place afalse busy guard, preventing the seizure of any of the selectors of thegroup to other simultaneously hunting line switches, otherwise adaptedto be seized. On the other hand, when the common conductor 216 becomesgrounded while the apparatus unit A is busy, as set forth, all idleselectors of the group embraced by the said apparatus unit 'will becomefalsely guarded against seizure thereby, bearing in mind that selectorsof the latter said group which are actually busy, will be guardedagainst seizare by reason of the private conductor there ofcorresponding to 553 constituting ground. Manifestly, a selectorembraced by the apparatus'unit A, for example, muf t not be seizableunless the said ap )aratus unit is free, as otherwise there won (1 be nomeans to adapt the seized selector to make it responsive to directivecontrol.

In view of the tone source DT being in the traced path including thelower winding of relay 151 and the receiver of-the calling substantion Tthe calling party will know that an idle selector has been seized, andthat the embracing apparatus unit has operatively associated itself, sothat directive calling may be forthwith proceeded ,with.

Returning to the condition wherein the call was completed to theselector S, where- 405,'respectively, and to the connector C,'

ground being maintained on conductor 402 from the said connector in thewell known manner. Then, upon the last two digits 11 being sent, theconnector C will function in the well known manner to extend theconnection to thesubstation-T, the line cut-offrelay LOO operating inthe well known manner. Armature 170 in apparatus unit A, and armature525 in line switch l) being attracted, and the vertical off-normalsprings VO being operated, no ground exists on the common conductor 216,nor on common conductor 215, due to the latter stated condition withreference to the vertical off-normal springs.

Should the calling party replace the re-' ceiver, thereby deenergizingthe line relay in the connector (1, whereupon the conductor 402 willbecome ungrounded, the latter said connector will restore in the wellknown manner, as well as selector 8*. Due to relay 155 in theapparatusunit having deactuated consequent to relay S actuating to effect theseizure of selector B the lower winding of relay S is unenergized, sothe latter said relay will now deactuate because the removal of groundfrom conductor 402 unenergizes the upper winding of said relay S Thelatter function opens the sustaining ground to relay 527 in the lineswitch D received from armature 220. It also closes a circuit from therelease magnet Re ofl-normal actuated to keep the windings of the linerelay 151 disassociated from the said established connection, it will beassumed that a call is initiated from substation T and that falselyguard all selectors (except the latter selector C is seized as the firstavailable idle selector. In view of the fact the line switches I) and Dare similar, and that selectors B and C are similar and correspondinglydrawn, it is thought unnecessary to a clear understanding to describe indetail the operations with respect to the functioning"consequent to thecall being initiated and the selector C being seized by the line switchof the calling substation. Sufiice it to state that common conductors215 and 210 become grounded, the former said conductor to initiate theoperation of the motor magnet M, and the latter said conductor to saidseized collector C, which is now. guard ed through its privateconductor) embraced by the apparatus unit A against seizure, if notbusy.

The relay S in selector C will actuate as in the manner of relay S?described, consequent to the line switch E seizing the selector C therelays S and S being alike. This will apply ground from the verticaloff-normal springs of set V0 armature 313, conductor 314 to bank contact126', accessible to wiper 146 of the apparatus unit A, being the setfirst successively engaged by wiper 146 upon it rotating from bankcontact 126, due to conductor 215 becoming grounded by reason of theattraction of armature 312 of relay S Conductor 216. ,will also begroundedfrom armature 312. The ground from conductor 215 will energizethe motor magnet M over the path before traced, so that the wiper set135 to 147 will be advanced from the bank contact set 115 to 127 to thenext successive bank contact set 115' to 127. The latter said set ofbank contacts have the same relation to selector C that the precedingsaid set has to selector B Upon the wiper 146 engaging the bank contact126, the ground on the latter will be communicated to the winding ofrelay 148, causing the latter said relay to actuate. The armature 113attracting, opens the energizing path described to the winding of themotor magnet M, thus disabling the latter said magnet from furtherautomatically and vancing the set of wipers 135 to 147 from the set ofbank contacts 115 to 127.

When the motor magnet M-operates, its armature 180 applies its ground tothe winding of relay 179 for the purpose of maintaining the windings ofrelay 151 disassociated from the wipers 135 and 145, as otherwise thesaid windings would become associated with passed-over talkingconductors of busy connections, causing disturbance. The relay 17 9 ismade slow-releasing so that it will sustain over current lapses whilethe armature 180 is in a retracted state for the brief periods in thehunting operation. In View of the delay of establishing the windings ofrelay 151 to wipers 135 and 145 after the set of wipers have stop edupon the set of bank contacts correspon ing to the selector embraced byapparatus unit A last seized, a set of supplemental contacts is providedon relay 148 which will forthwith apply the windings of relay 151 towipers 135 and 145 upon the set of wipers being stopped due to wiper 146encountering ground, as set forth. before the relay 148 will, preventingthe windings of relay 151 being falsely disconnected when the seizedselector has once become in readiness to receive directive control. Itwill appear, that while the apparatus unit A has its wipers resting u ona bank contact set corresponding to a se ector which has seized thesecond selector, as for example, when the selector B seized selector S",the attracted condition of armature 209 causes ground to be appliedthrough rotary off-normal springs, conductor 222, bank contact 127,wiper 147 to the winding of relay 179, before referred to. This willinsure that the windings of relay 151 will be disassociated from thetalking conductors leading through the selector 13*. Of course, if theselector B becomes idle, and the ground is removed from the bank contact127, the relay 179 will deactuate to re-associate the windings of relay151.

In relation to the call initiated from substation T, forthwith upon therelay 148 actuating upon the wipers 135 to 147 engaging bank contacts115' to 127, the tone from source DT will be perceived, indexing thatthe directive operation of the selector C can be proceeded with, whereinthe functioning will be as has been fully described with relation tosubstation T line switch D and selector B'-, the now concerned circuitsand equipments being duplicates thereof, having due regard to the factthat the trunk to selector S is busy, so that an alternative trunk, (notshown) will be seized. Assuming that the last three digits will be1-1-1, as before, the alternative selector terminating the saidalternatively seized trunk will seize an alternative connector of thegroup containing connector C (but not shown), and the latter willencounter the called line leading to substation T as busy, applying thebusy tone over the talking conductors in the well known manner. The established connection will be destroyed by replacing the receiver atsubstation T, as if the call had been completed to the called line, byreason of the fact that ground received from connector C will be therebyremoved from wiper 303. The detailed operation of the selector C in thisconnection, and under its various operative conditions, will be fullycomprehended in view of the fact that corresponding elements in Fig. 3

are designated with the index digit 3 to The relay 179 will deactuate'correspond to the designations in Fig. 2, wherein the index digit 2 isused, and in view of the fact corresponding elements in Fig. 6 aredesignated with an index digit 6 to correspond to designations in Fig.5, wherein the index digit 5 is used. Designations in Fig. 1 which referto selector C have a prime added to distinguish from correspondingdesignations thereon which referto selector B It will be assumed thatafter the line switch D seized selector B and the wipers 135 to 147 haveengaged bank contacts 115 to 127, and before any directive impulses weresent, the receiver at substation T is replaced. Relays 151 and 155 willretract, they having attracted consequent to the wipers 135 to 147engaging bank contacts 115 to 127. This will remove ground from thelower winding of relay S so the armature 209 (and armatures 211,212 and213) will retract, completing the traced path from ground to the windingof the release magnet Re WVhen the relay 155 deactuates, causing relay Sto fully retract all its armatures, relay 148 will deactuate. However,if in place of restoring the receiver, as assumed, directive impulseshad been sent, as was formerly assumed, the vertical oil-normal springset would be operated, incidentally deenergizing the relay 148. Theground applied to the live terminal of the upper winding of relay S willbe removed before relay 167 has been operated and then caused to retractits armature 169, so the armature 181 will not be attracted under thecondition of armature 171 locking under the condition of the selectorhunting, as otherwise the rotary magnet RM would be caused to advanceafter relay 170 unlocked incidental to the ungrounded bank contact beingfound by Wiper 203. I

It will be assumed that at the time the call is initiated fromsubstation T the wipers of the apparatus unit in place of being inengagement with the set of bank contacts corresponding to the selector Basshown in the drawings, has its wipers resting upon the bank contactscorresponding to the selector C Upon the selector B being seized by theline switch D the described condition is setup, which it will beremembered included the grounding of common conductors 215 and 216, andthe grounding of individual conductor 214; the latter for the purpose ofdisabling the motor magnet M upon the wipers of the apparatus unit Aengaging the set of bank contacts corresponding to selector B all otherselectors of the group embraced by the apparatus unit A being barredagainst seizure by a line switch due to the grounded condition ofconductor 216, and which condition will endure until relay 155deactuates after selector B seizes' second selector S, notwithstandingthat the ground primarily applied to. conductor 216 from armature 212was disconnected incidental to the first off-normal movement of .seized,notwithstanding the calling party has replaced his receiver. It willappear presently that the relay S will be unlocked, whereby the lineswitch D will be restored, so that the equipments are normal, and idleselectors of the group embraced by the apparatus unit A will be subjectto seizure. Upon the wiper 146 engaging bank contact 126 and receivingground therefrom through armature 213, relay 148 will actuate and applyground through its armature 181, wiper 138, bank contact 118, conductor172 to the live terminal of the upper winding of relay S causing thelatter said relay to completely retract all of its armatures, sincethere is no energizing path for the wind ings of relay 151, so that therelay 155 remains deactua-ted. Under this condition, the lower windingof relay S does not become energized upon the wipers of the ap paratusunit A engaging the bank contact set corresponding to selector B Iheolfnormal spring set V0 not having actuated, no circuit path iscompleted to the release magnet Re though the relay S is now un locked,and the line switch D is unseized. The idle selectors of the groupembraced by apparatus unit A are now subject to seizure by a huntingline switch.

In View of the foregoing, it .will appear that the object of armature181 is to forthwith provide a set-up condition in the selec- 1 tor withwhich a line switch becomes associated, so that in the event the callingparty replaces his receiver before the apparatus unit A has had time toassociate itself with the latter said selector, or before the lattersaid selector seizes a second selector, a means will be provided torestore the latter said selector through causing its relay to fullydeactuate.

The exampled application of the present invention is but one of manyapplications thereof, the invention being subject to wide modificationswithout departing from the scope of it, defined by the subjoined claims.

I claim 1. In a telephone system, a group of selective switches, adriving control relay set for said switches common thereto, andselective means responsive to seizure of any one of said switches forselecting the seized switch and connecting the relay set thereto,

the said relay set remaining connected with the. said seized switchuntil a seizure of another'one of said selective switches occurs.

2. Ina, telephone system, a group of selective switches, a drivingcontrol relay set for said switches common thereto, selective meansresponsive to seizure of any one ot'. said switches for selecting theseized switch and connecting the relay .set thereto, and. meansautomatically operative following theoperation of the said selectiveswitch to cperatively disconnect the relay set there from and render itavailable for connection with another one of the switches of the andconnecting the relay set thereto, means automatically operativefollowing the oper ation of the said selective switch to operativelydisconnect the relay set therefrom and render it available forconnection with another one of the switches of the group,

the said relay set remaining connected with the said seized switch untila seizure of another one of said selective switches occurs, and meansresponsive to seizure of another one of the selective switches of thegroup while the first one is still busy to reoperate said selectivemeans to connect the driving control relay set to the last selectedswitch.

4. In a telephone system, telephone lines, a group of selectiveswitches, means for seizing said switches by said lines for extendingcalls from said lines, a common driving control relay set for saidswitches, and selective mechanism for temporarily connecting the relayset to diiferent ones of said switches responsive to seizure ofrespective said switches in extending successive calls thereaftersimultaneously existing, the said connecting being maintained until asuccessive said seizure.

5. In a. telephone system, telephone lines, selective switches forextending calls from said lines, automatic switches for connectingcalling lines and the selective switches, a common driving control relayset for said selective switches, selective mechanism responslve toconnections of said automatic switches for temporarily connecting the relay set to different ones of said selective switches during therespective driving period, and means for successively operating saidselective mechanism responsive to suecessive calls for successivelyconnecting said relay set to successively selected said automaticswitches whether or not the extended calls are simultaneously existing,the sa d connecting being maintained until a successive call.

6. A selective switch having driving apparatus, control relays therefornormally operatively disconnected therefromand tem-' porarilyoperatively connected therew th during the driving period, but notmdividual thereto, means for temporarily operatively connecting thecontrol relays w th the said switch, and means for operativelydisconnecting the control relays forthwith after each driving period foruse 1n a new call, but leaving the said sw1tch operated, the controlrelays remaining specifically related to the switch. 0

7. A selective switch having driving apparatus and control relaystherefor temporarily operatively connected therew1t h during the drivingperiod, but not individual thereto, means for operatively connecting thecontrol relays with the sald switch, and means automatically operativefor operatively disconnecting the control relays forthwith after eachdriving period for use 1n a 'new call, but leaving the said switchoperated, and the control relays inoperatively connected with theselective switch.

8. A selective switch having driving apparatus and control relaystherefor temporarily operatively connected therewitlrduring the drivingperiod, but not lndlvldual thereto, cooperating sw1tches, mean s madeoperative consequent to the sa1d sw1tch becoming seized by asaidcooperatmg switch for operatively connecting the control relays withthe said selective switch, and means antomatically operative fordisconnecting the control relays forthwith after each drlving period foruse in a new call, but leaving the said switch operated and the controlrelays inoperatively connected with the last said switch.

9. In a group of selectors, each selector having a permanentlyassociated means for operating its wipers responsive to d rectivecontrol relays applied to its leadmg-in conductors, a temporarilyconnected means common to the group for correlating the directivecontrol relays with the permanently associated operating meansconsequent to a selector of the group becoming seized, and means forreleasing the control relaysafter each operating period for associationwith another selector for use in a new call, but leaving the operatedselector in its actuated position and the control relays inoperativelyconnected with the said operated selector.

10. In a telephone system, a plurality of selective switches havingindividual driving mechanisms, a control relay set, means fortemporarily connecting the relay set with one of the selective switchesconsequent to the last said selective switch becoming seized, andautomatic means made operative forthwith upon the termination of thedriving period of the said selective switch for disconnecting the saidcontrol relay set from a connected said selective switch for use in anew call, leaving the control relay set inoperatively connected with thelast said selective switch.

11. In a telephone system, a plurality of selective switches havingindividual driving mechanisms, a control relay set common to saidswitches, means for seizing an idle said switch, hunting means madeoperative consequent to the seizing of the said switch to cause thecontrol relay set to selectively connect itself with the seized saidswitch and to thereafter operatively disconnect itself upon the seizedsaid switch itself seizing, while retaining its inoperative connectionwith the lastsaid switch.

12. In a telephone system, calling lines, a plurality of selectiveswitches having individual driving mechanisms, a control relay setcommon to said switches, selective means for associating the controlrelay set with any of said selective switches, means for linking acalling line to a said selective switch, means operative consequent tothe said linking operation for barring other said selectors againstseizure by way of linking a second calling line, means for causing thecontrol relay set to be connected with the said selective switchresultant to it becoming linked, and means made operative consequentto'the termination of the driving period of the selective switch forunbarring the said barred switches and for disabling the control of thecontrol relay set from the. selector last using it.

13. In a telephone system, calling lines, a plurality of selectiveswitches having individual driving mechanisms, a control relay setcommon to said switches, selective means for associating the controlrelay set with any of said selective switches, means for linking acalling line to a said selective switch, means operative consequent tothe said linking operation for barring other said selectors againstseizure by Way of linking asecond calling line, means for causing thecontrol relay set to be associated with the said selective switchresultant to it becoming linked, and means operative contequent to thetermination of the driving period of the selective switch for unbarringthe said barred switches and for operatively disconnecting the controlof the control relay set from the selector lastusing it, restoring thecontrol relay set subject to the control of the first said selectiveswitch to become linked to a selective switch thereafter, whileretaining its inoperative connection with the last said switch operated.

3 :14. In a telephone system, a plurality of line switches, a pluralityof selective switches subject to being seized by the line switches, acontrol relay set, means for connecting the said set with any saidswitch seized to adapt the said seized switch to be subject to directivecontrol and to bar the other of the said switches against being seized,means for controlling the said seized switch whereby it will seize anaccessible line, and means made operative consequent upon the saidswitch seizing the said line whereby the said bar is removed from thesaid other switches and the said set is rendered subject to the controlof the first of the said switches thereafter seized.

15. In a telephone system, a group of'selective switches, a drivingcontrol relay set as a component element of the respective said switchescommon thereto, selective means responsive to seizure of any one of saidswitches for selecting the seized switch and connecting the relay setthereto, and audible indicating means automatically operative consequentupon the driving control relay set becoming connected with the seizedswitch.

1 6; In a telephone system, a group of selective switches, a drivingcontrol relay set as a component element of the respective said switchescommon thereto, selective means responsive to seizure of any one of saidswitches for selecting the seized switch and connecting the relay-setthereto, and a tone source and means for applying it to the talkingcircuits of the said switch upon the relay set becoming connected to thesaid switch.

17. In a telephone system, a group of selective switches, a drivingcontrol relay set for said switches common thereto, a hunting means madeoperative responsive to the seizure of a said switch for connecting thesaid relay set to the exclusive use of the said seized switch, and meansautomatically self initiated forthwith following the full operation ofthe seized selective switch to disconnect the said driving control relayset from operative control thereof and to thereupon render the drivingcontrol relay set in control of any one of the switches of the groupirrespective of whether or not there is another call to the last saidswitches or whether the hunting means has reoperated.

18. In a telephone system, a group of selective switches, a'drivingcontrol relay set for said switches common thereto, a hunting means madeoperative responsive to the seizure of a said switch for connecting thesaid relay set to the exclusive use of the said seized switch, meansautomatically self initiated forthwith following the full operation ofthe seized selective switch to disconnect the said driving control relayset from operative control thereof and to thereupon render the drivingcontrol relay set in control of any one of the switches of the groupirrespective of whether or not there is another call to the last saidswitches or whether the hunting meanshas reoperated, and meansresponsive to the seizure of 'another one of the selective switches ofthe group while the first one is still busy to bar any idle selectiveswitches of the group against seizure.

19. Iii a telephone system, a group of selective switches, a drivingcontrol relay set for said switches common thereto, a hunting means madeoperative responsive to the seizure of a said switch for connecting thesaid relay set to the exclusive use of the said seized switch, meansautomatically self initiated forthwith following the full operation ofthe'seized selective switch to disconnect the said driving control relayset from operative control thereof and to thereupon render the drivingcontrol relay set in control of any one of the switches of the groupirrespective of whether or not there is another call to the last saidswitches or whether the hunting means has reoperated, and meansresponsive to the seizure of another one of the selective switches ofthe group while the first one is still busy to bar.

any idle selective switch of the group against seizure, until the lastseized selective switch has been fully operated. a

20. In a'telephone system, a plurality of groups of trunking switches, aplurality of groups of trunk lines each line leading to one of saidtrunking switches, a common control relay for each group of trunkingswitches normally operatively related thereto, groups of calling linesleading to groups of corresponding selective switches, each of thelatter said switches having access to a said group of trunking switches,the groups of trunking switches and the groups of selective switches notcorresponding, each of the said selective switches having access to onlyone trunking switch related to a common relay.

21. In a telephone system, a plurality of groups of trunking switches, aplurality of groups of trunk lines each line leading to one of saidtrunking switches, a common control relay for each group of trunkingswitches normally operatively related thereto, calling lines leading toselective switches, each of the latter said switches having access to asaid group of trunking switches, each of the said selective switcheshaving access to only'one trunking switch related to a common relay.

22. In a telephone system, a plurality of groups of trunking switches, aplurality of groups of trunk lines each line leading to one of saidtrunking switches, a common control relay for each group of trunkingswitches normally operatively related there to, groups of calling linesleading to groups of corresponding selective switches, each of thelatter said switches having access to a said group of trunking switches,the groups oftrunking switches and the groups of selective switches notcorresponding, each of the said selective switches having access to onlyone trunking switch related to a common relay, and automatic meansoperative upon a trunking switch becoming seized to associate its saidcommon relay into operative relation with it.

23. In a telephone system, a plurality of groups of trunking switches, aplurality of groups of trunk lines each line leading to one of saidtrunking switches, a common control relay for each .group of trunkingswitches normally operatively related thereto, calling lines leading toselective switches,

, ,each of the latter said switches having access to a said group oftrunking switches, each of the said selective switches having access toonly one trunking switch related to a common relay, and automatic meansoperative. upon a trunking switch becoming seized to associate its saidcommon relay into operative relation with it.

24;; In a telephone system, a plurality of groups of trunking switches,a plurality of groupsof trunk lines eachline leading to .one of saidtrunking switches, a common control relay for each group of trunkingswitches normally operatively related thereto, groups of calling linesleading to groups of corresponding selective switches, each of thelatter said switches having access to a said group of trunking switches,the groups of trunking switches and the groups of selective switches notcorresponding, each of the said selective switches having access to onlyone trunking switch related to a common relay, automatic means operativeupon a trunking switch becoming seized to associate its said commonrelay into operative relation with it, and means operative incidental tothe seizure. by a said trunking switch to disconnect its Said relay fromoperative relation with it.

25. In an automatic telephone system, a group of selective switches, adriving control relay set for said switches common thereto, a fixed setof terminals for each switch cooperative for being swept with a set ofmovable terminals of the said relay set, a hunting means made operativeresponsive to the seizure of a said switch for connecting said relay setthrough a said fixed set of terminals and thereby setting the saidmovable set of terminals for the exclusive use of the said seizedswitch, an impulse relay of the said set for operative control of theselective switch with which the said relay set is set, and means fordisabling the said impulse relay from affecting passed over terminalsduring the said hunting operation.

26. In an automatic telephone system, a

line switch, a first selective switch at normal, leading-in talkingconductor terminals for said first selective switch, a busy conductorterminal for said first selective switch, a relay in the said firstselective switch operative responsive to a circuit path closureincluding the busy terminal by the line switch, a second selectiveswitch, means for setting the first selective switch into connectiverelation with the said second selective switch, means in the, secondselective switch for maintaining the said. relay energized, and meanscontrolled over the talking conductors for deenergizing the relay.

27. In a telephone system, a group of selective switches, a drivingcontrol relay set for said switches and component thereof,

selective means responsive to the seizure of" any one of said switchesfor selecting the seized switch and for connecting said relay setthereto, and means for retaining the selective means in its selectedposition until another one of said switches is seized.

28. In a telephone system, a group of selective switches, a drivingcontrol relay set for said switches and component thereof, selectivemeans responsive to the seizure of any one of said switches forselecting the seized switch and for connecting said relay set thereto,means for retaining the selective means in its selected position untilanother one of said switches is seized, and means responsive to againseizing said seized switch in a new call for re-connecting the relay setthereto without re-operating said selective means.

29, In a telephone system, a group of selective switches,'a drivingcontrol relay set for said switches common thereto, selective meansresponsive. to seizure of any one of said switches for selecting theseized switch and connecting the relay set thereto, and means responsiveto re-seizure of said seized switch in a new call for re-connecting therelay set thereto without re-operating said selective means.

30. In a telephone system, a group of selective switches, a drivingcontrol relay set for said switches common thereto, selective meansresponsive to the seizure of any one of said switches for selecting theseized switch and for connecting said relay set thereto, means forretaining the selective means in its selected position corresponding tothe switch seized until another one of said switches is seized, andmeans thereupon operative to re-operate the selective means from itssaid position to select the said another switch seized and forconnecting said relay set thereto.

31. In a telephone system, a group of selective switches, a plurality ofdriving control relay sets for said switches common thereto andcomponent thereof, and selective

